Piston cooling



Oct. 20, 1942.- R. H. SHEPPARD 2,299,506

' PISTON COOLING Filed Jan. 15, 1942 M N I z.

z A 2 g E '7 1 r y /7 /6 S A? I i I 2/ I I I 7 Z Patented Oct. 20, 1942 UNITED STATES PATENT OFFICE PISTON COOLING Richard H. Sheppard, Hanover, Pa.

Application January 15, 1942, Serial No. 426,903

7 Claims. (01. 123176) This invention relates to Diesel engines and has for its principal object the provision of a piston crown cooling system wherein the oil spray is concentrated at the hottest part of the piston, which is directly under the combustion chamber.

A further object of the present invention is to increase the length of life of the rings, liners, and pistons of Diesel engines operating at high speeds and high pressures, by directing the cool fluid to that portion only of the piston crown which is most highly heated thus providing a lowered maximum temperature with a consequent minimizing of unequal piston expansion.

In the drawing which shows a typical example of the use of my system: 7

Figure 1 is a central section through the cylinder piston and pre-combustion chamber of a Diesel engine.

Figure 2 is a bottom plan view taken throug the axis of the wrist pin.

Pre-combustion chamber I is formed in part by a plug I I, here shown as a cylinder but which may be of any other normal shape. In the plug II are a series of throats I2, I3 and I4, for discharging hurtling fuel from the combustion chamber to the cylinder in well known manner. The piston [5 may be of any suitable type and is provided with the usual wrist pin indicated by the numeral l6, surrounded by the head I! of a connecting rod. The details of the connecting rod and the cylinder I8 are purposely left unshown in order to emphasize the fact that the invention is to be considered broadly.

Within the piston head are radially disposed spray nozzles l9 and 20, positioned at such angles as to concentrate the discharge of the cooling oil admitted through the passage 2| in the center of the hollow connecting rod, in the usual manner, so that the portion of the piston crown directly under the plug H is cooled as the heat is applied thus tending to make the temperature of the piston crown quite uniform. This equalizes the distribution of the heat throughout the piston head and prevents, or at very least minimizes, the tendency toward unequal piston expansion, due to the fact that in absence of the present system the portion to the left in Figure 1 will be appreciably cooler than the portion to the right. This naturally holds good whenever the entire piston crown is cooled as is the usual practice.

Assuming a connecting rod length of about eleven inches, center to center, and a throw of 2 inches, I find the best angle for locating the two oil spray angle nozzles as 22 and 29,

respectively from the plane 22 which contains the wrist pin axis and the piston or cylinder axis. With the length. and throw stated the oscillation of the connecting rod head will be about 13 so that as the two nozzles are illustrated the cooling oil spray extends from a point such "as 23 at the junction of the plug and cylinder to a point such as 25 which is about half-way between vertical and horizontal. The angle between plane 22 and the nearest approach of the spray from the proximate nozzle may run to zero or beyond, but I prefer the angle indicated which is about 9 which gives a range of path from 9 to 42, plus the half-width of a single spray. The width of this path which lies on both sides of a plane at right angles to the plane 22 may be varied as desired by a slight tapering of the orifices I9 and 20. I prefer, however, that these nozzles be cylindrical and find a diameter of about .07" gives the best results.

The idea of cooling a piston head by oil is old and well known, and the novelty of the present invention lies in the fact that the spray is shaped and concentrated so that the piston crown is cooled where it needs it most. The holes in the top of the connecting rod spray the oil back and forth over the hot spot of the piston as the rod oscillates giving the great advantage in that the cooling oil removes the heat as fast as it is applied to the piston and from the point at which the heat is concentrated. This directional cooling equalizes the heat and permits the use of much closer fitted pistons than is possible with an undirectional cooling oil spray. Not only may I use smaller tolerances than has previously been used but I find with spray the cooling oil in the path indicated by the dotted line 36, which is roughly the hot spot on the piston, the life of the rings, liners, and pistons have been surprisingly lengthened and the oil consumption has been reduced to a very low figure corresponding roughly with from three thousand to five thousand miles per quart of oil in an automobile.

What I claim is:

l. A connecting rod for use with a piston for a Diesel engine cylinder in which the jets from the combustion chamber discharge into the cylinder to one side of a plane passing through the pistonvand wrist pin axes, characterized by the provision of oil discharge means in the head of the connecting rod, directed so as to spray cooling oil under pressure against the inside of the piston crown in a path at right angles to said plane and in the direction of said fuel jets, whereby the piston crown is cooled directly under the combustion chamber and minimizes unequal piston expansion due to unequal distribution of heat in the piston crown.

2. The device of claim 1 in which the means includes a plurality of radial orifices.

3. The device of claim 1 in which the means includes a plurality of orifices centrally positioned in the head of the connecting rod, and making an angle with said plane of not less than 20 and not more than 35 respectively from said plane when the connecting rod is at dead centers.

4. A connecting rod for use with a piston for a Diesel engine cylinder having a plurality of fuel jets all located to one side of a plane passing through the piston and wrist pin axes, characterized by the provision of a plurality of oil discharge orifices in the head of the rod directed so as to spray cooling oil under pressure against the inside of the piston crown in a path at right angles to said plane in a range including from 20 to 35 from said plane.

5. The device of claim 4 in which one orifice is positioned at an angle of about 22, and the aeoasoe second orifice is at about 29 from said plane when the rod is at dead centers.

6. The device of claim 4 in which there are two orifices centrally positioned. in the head of the rod positioned not exceeding 15 apart, Whereby to throw a spray roughly 45 thus cooling the hottest part of the piston crown.

7.121 combination, a Diesel engine having a cylinder, a pro-combustion chamber plug having a diameter less than half of the diameter of the cylinder, said pre-cornbustion chamber plug being offset from said cylinder and axis and positioned to have ignited fuel jets therein discharging into the cylinder, a piston in said cylinder, a connecting rod having one head oscillatingly mounted within the piston, means for directing cooling oil under pressure against the inside of the piston crown directly beneath said plug, whereby the heat is removed from the hottest portion of the piston and thus minimizes unequal distribution of heat in the piston and thus lessening the tendency of the piston rings to stick at high speeds and high pressures.

RICHARD H. SHEPPARD. 

